Reactive thermal spraying of alumina and zircon mixtures to form mullite composites

Mullite (3A1203- 2Si02) is a strong candidate for advanced structural applications at both low and high temperatures because of its high strength at high temperatures, low thermal expansion, excellent creep resistance, and good chemical stability. Besides its importance for conventional ceramics, mullite has become a strong candidate material for advanced structural and functional ceramics in recent years. A very broad application field for mullite material is considered for the future. However, the relative poor mechanical properties at low temperatures and difficulty in processing have prevented a more widespread use of this ceramic material. Zirconia(Zr02) addition is found to be effective in improving the strength and fracture toughness of mullite at intermediate temperatures. The present study has attempted to form ZrCV toughened mullite by mechanical alloying (MA) and plasma spraying of high purity alumina (AI2O3) and zircon (ZrSiC^) mixtures. The feedstock was prepared by a combination of mechanical alloying which allowed formation of fine grained, homogeneous solid solution mixtures, and following plasma spheroidization that yielded rapidly solidified microstructures and enhanced compositional homogeneity.Doctor of Philosoph